meimei I'm glad you managed to get a digicam and have photos of your visit! I lost my iPhone when I went to Lisbon on our second-to-the-last day (t**** lang kase, naiwan ko yung charger for my digicam huhu) and so all my pictures were gone! Hindi talaga maganda ang feeling. It's good you managed to have visual memories!
Once is actually a very nice production.

And that's the usual price of cabs that you should be paying for airport transfers! How much ulit yung arrival mo? 70+ ba yun? That was a joke!
blaire.witchHmmmmm. *mega isip* Like I said, I have no idea about accommodation in this city, and can only recommend
Palmers Lodge Swiss Cottage dahil I pass by it often hehe. Also Key from SHINee (Korean boy band) stayed there when he visited! Haha. Anyway, it's a hostel and in a quiet neighborhood (look up Hampstead), but I'm recommending it because of the proximity to Swiss Cottage tube station (less than 5 minute walk) and bus stops. If day 1 is the day you arrive, it might take a bit of time getting there, but you can take the tipid route and use the tube -- it takes roughly 45 minutes to an hour from Heathrow to Swiss Cottage station. Maybe 30-40 minutes by cab (I remember paying around 35 or 38 pounds?)
Your
day 1 sounds okay, because like sis meimei said, those are all very near to each other. Hyde Park is bigger than St. James Park (which is admittedly more charming), although Hyde Park is right next to Kensington Gardens which is pretty in its own right. The Tower Bridge (aka London Bridge -- the locals will sniff at you if you call it that

) is a bit out of the way, but it's very good to see. If you had more time, I definitely recommend it. I don't suggest queuing up at London Eye -- long queues, quite expensive for the low entertainment -- it gets boring after a while up there. If you wanted views of London -- FOR FREE! -- just get to the top of Primrose Hill and it has beautiful views of the city.
SO! If you stay at Palmers Lodge, Primrose Hill is a 10-15 minute walk from it. And for your day 1, you can take the train (from Swiss Cottage) all the way to Westminster station (takes less than 15 minutes from a rough estimate), and you come out right next to Big Ben, the Parliament buildling, and a nice view from the bridge of the London Eye (you can walk there too if you like, less than 10 minutes). When you're done doing photos, walk down Whitehall towards the Horse Guards Palace (you'll pass by 10 Downing Street but the street is actually guarded so you can't even take a photo in front of it), and take photos with the Queen's Guards (some of them on horses). You can walk down the Mall para tumbukin niyo ang Buckingham Palace, or you can take the one with a view and go through St. James Park and still come out in front of Buckingham Palace. (Change of guards happen at 11 AM, if you wanted to witness that). You can take a bus or the train to Piccadilly Circus, where you can have a quick dinner in Soho before catching Miss Saigon (lots of good restaurants there).
Day 2 would depend what time your tickets for Harry Potter are. I can't remember when I went; may morning and afternoon sessions ba? Anyhow, it's right in the outskirts of London, so it's a bit malayo. I remember that took up most of the day when I visited, because of the travel time. If you get up really early, you can head off to Abbey Road (20-25 minute walk depending on your speed hehe) or again, take the tube (it's just one stop from Swiss Cottage to St.John's Wood) or a bus (cheaper), take pictures on the pedestrian (this is difficult because it's a usable road so cars do drive through it, but they do respect the zebra crossing here). You can then get a bus again all the way up to Finchley Road to get the Overground train via the Finchley & Frognal station. You'll have to change to a different train in Willesden Junction to head to Watford Junction, and there's a bus there to take you to Leavesden Studios. Nothing happens in Watford, so don't waste your time exploring that part! Hehe.
Ang out of the way lang is Notting Hill. It has a nice vibe that I think you'd appreciate seeing/experiencing, but the Harry Potter tour takes away a lot of your time kase. It took me around 2-3 hours soaking in Portobello Road, and that was because we just walked down the street and looked at wares.

There are trains to Bath from Paddington, which is a 20-minute bus ride from Palmers Lodge if you do decide to stay there.
SORRY, ANG HABA! But yeah, since you mentioned Harry Potter and Abbey Road, this area is great due to the proximity of train stations (you have four different train stations on different lines less than 10-15 minutes walk from where you stay!)